FIG. 1A shows a schematic representation of an exemplar actuator. The actuator of FIG. 1A is an electromagnetic actuator. The actuator includes a casing 103, two coils 104, two springs 105, rubber cushions 102, a moving element (ME) 101, and a fixed element 100.
Usually, the ME 101 comes in contact with the fixed mechanical element 100 when the actuator is not actuated. To move the ME 101 towards the casing 103, the actuator system is actuated by injecting a current in the coil 104. When the current is cancelled, the ME is pushed against the fixed element 100 by a spring force generated by the springs 102 positioned between the actuator casing 103 and the ME 101. To dampen the contact force, rubber cushions 102 are inserted between the ME and the casing.
FIG. 1B shows another example of the actuator used in an elevator brake system. In this example, a fixed element 110 is curved and represents an elevator brake wheel 120. The fixed element that comes in contact with the elevator brake system is called an elevator drum. Usually, the elevator wheel has two symmetrical elevator brake systems 130. The two elevator brake systems are identical and similarly controlled. For illustration purposes, the elevator brake system is enlarged 140, and schematically shown 150. The ME 155 is also curved to be consistent with the shape of the elevator drum. The rest of the system elements remain in place.
The elevator brake system should be capable of developing relatively large torques and be able to quickly stop the elevator car and counterweight. Additionally, brakes systems can be located near building occupiers, so quiet brake operation is necessary. Furthermore, because the location of the brakes is not always easily accessible, an emphasis is placed on a reliable brake system that is easy to adjust and maintain.
In one method [U.S. Pat. No. 5,717,174], the brake is controlled by position sensor feedback, and the controller adjusts the voltage signal controlling the ME motion to minimize impact velocities. However, there is no quantitative prediction of the achievable performances with respect to the system aging. Moreover, the electronic circuit controls the brake ME in both directions, against the spring force to slowdown the ME motion, and towards the spring force to accelerate the ME motion towards the drum.